Magnet-steel



No Drawing.

UNITED STATES PATENT OFFICE.

KOTARO HONDA, OF YO NEGA-FUKURO, SENDAI, JAPAN, ASSIGNOR TO SUMITOMO CHUKOSHO, LTD, OF OSAKA, JAPAN, A CORPORATION OF JAPAN.

MAGNET-STEEL.

To all whom it may concern Be it known that I, Ko'rAno I'IONDA D. Sc., citizen of Japan, residing at No. 21,l(anoko Shimidzu, Yonega-fukuro, Sendai, Japan, have invented certain new and useful Improvements in Magnet-Steel; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same. 1

This invention relates to novel magnet steels and to magnets made therefrom. More particularly, the invention relates to the manufacture of permanent magnets from alloys comprising carbon steel, cobalt,

and a metal of the chromium family. Magnets made in accordance with the invention materially excel magnets heretofore known especially in point of strong residual. magnetism and large coercive force.

In the particular embodiment of themvention herein disclosed and. claimed, the

metal chromium itself is an essential ingredient of the alloy steel employed. In my copending application Serial No. 197,837,

filed October 22, 1917, the generic invention,

of which the present application covers a specific phase, is broadly claimed.

In a typical instance, a magnet embodying the principles of the invention may be made of an alloy steel having the following ralge of composition:

obalt, 5-6070; chromium, 05-10%; a.-

bon steel, (with.O.5-2% carbon,) the remainder. Most desirably the cobalt content is from 20 to and 35% has been found particularly suitable. Other elements commonly present in steel may also be present in the alloy, and vanadium or the like may also be added.

In manufacturing-this alloy steel, a mixture of the above-mentioned metallic ingredients may be melted at a temperature of, say 1700 to 1800 (l, and poured to form an ingot. When sufiiciently cooled the ingot is forged and worked into the form of a magnet, and is then hardened as by quenching at a temperature of say 1100 0., for example, this temperature being consid- Specification of Letters Patent. Patented Apr. 27, 1920.

, Application filed October 22, 1917. Serial No. 197,838.

erably higher than the quenching tempera ture for ordinary magnet steel which is about 800 C. After quenching, the shaped body of paramagnetic metallic material is. strongly magnetized with the aid of a powerful magnet or coil.

The magnet produced in the manner described is far superior to magnets heretofore known in the art, particularly as regardsi (1) Coercive force which in magnets of the best (type heretofore known does not ex ceed 7 5 G. S. units, whereas in the pres ent magnet, the specific coercive force reaches 200 C. G. S. units. 1 For this reason, loss of magnetism orso-called magnetic decay, due to shock or lapse of time is exceed-z ingly small in the case of the present magnet.

(2) Intensity of magnetization per unit volume, which in the known magnets of the best type rarely exceeds 450 C. G. S. units 1. The method of preparing permanent magnets which comprisesv quenching at a temperature substantially above 800 C., a body of an alloy steel containing cobalt and chromium, and thereafter magnetizing said body.

2. As a new article of manufacture, a

magnetized body of an alloy steel containing cobalt and chromium.

3. As a new article of manufacture, a permanent magnet made of an allov containing from about 5 to 60 per cent. cobalt, from about 0.5 to 10 per cent. chromium and carbon steel of from about 0.5 to 2 per cent. carbon.

In testimony whereof I hereunto afiixmy signature.

KOTARO HONDA. 

